1. Field of the Invention
The present invention relates to an integrated semiconductor device.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 7-263655 discloses an integrated optical device including a laser diode and an optical modulator integrated on a semiconductor substrate. Each of the laser diode and the optical modulator has a stripe-shaped mesa structure. The mesa structure in each of the laser diode and the optical modulator has an optical waveguide structure including a core layer. The core layer of the laser diode and the core layer of the optical modulator are optically coupled with each other by a butt-joint method (butt-joint coupling).
A ridge waveguide and a mesa waveguide are well-known as a waveguide of semiconductor optical device. The ridge waveguide includes a ridge portion provided on a base portion. In the ridge waveguide, a core layer is included in the base portion. The mesa waveguide includes a semiconductor mesa. In the mesa waveguide, a core layer is included in the semiconductor mesa. As described in Japanese Unexamined Patent Application Publication No. 7-263655, the laser diode and the optical modulator have the same waveguide structure of the mesa structure.